From the HBD Archive
From: Darryl Richman <>
Subject: re: SG adjustments
Date: 1989-09-02 14:41:48 GMT

">and on Doug Roberts (HBD #236)
"> (T x 1.449E-4 - 0.009) + SG(uncorrected) = SG(corrected)
"This formula does not hold true for 60 degrees F. For 60 F I get a correction
"factor of -0.000306, decidedly not 0 as it should be for a hydrometer
"calibrated to read acurateley @ 60. I plotted the function using data
"points that I got out of the back of Byron Burch's Brewing quality Beers.
"The function that I was looking at was decidedly _not_ linear.

My goodness! Do you really think that your measurements are accurate
beyond 3 places on a hydrometer? (On my hydrometer, SG is marked off
in increments of .002, which means that I can only hope to read accurately
to about .001). Also, consider the size of the hair we are splitting
here: .0003 difference in OG corresponds to about .075% sugar in
solution. When fermented perfectly, half of this will go to alcohol.
My 3 scale hydrometer will definitely not allow me to measure the
difference. In fact, the owner of the shop I go to, who also owns
a Ventura county winery, has an ebulometer (a professinal lab device
for measuring alcohol content by distillation), and it is only good
for 2 decimal places.

--Darryl Richman

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